Water Soluble Polymersfor Immunoisolation I: Complex Coacervation and Cytotoxicity

Seventy five synthetic, semi-synthetic, natural and biological water soluble polymers have been evaluated as potential biomaterials for cell and islet immunoisolation. Measurements have included the cytotoxicity of polyanion and polycation solutions towards insulinoma cells as well as the type of complex coacervate interaction produced. These results have been coupled with metrics delineating the quality of the capsular membrane produced and correlated with molecular properties of the individual polymers tested. Microcapsules prepared from over one thousand binary polyelectrolyte combinations have been characterized according to their mechanical strength, capsule shape, surface smoothness, stability, and swelling or shrinking. Based on this screening 47 pairs have been identified as alternatives to the standard poly-l-lysine-alginate chemistry. The quality of the membrane produced was observed to be a strong function of the polymer molecular weight, as well as the solution concentration. Additionally, the ionic content of the backbone, the chemistry and location of functional group attachment, the chain rigidity, aromaticity, conformation and extent of branching were identified as important variables in the type of complex produced. The presence of secondary hydrogen bonding interactions was also found to be significant. Processing conditions such as the type and concentration of the simple electrolyte, the pH, the reaction time and surface coating have also been investigated.